Marine seismology companies invest heavily in the development of marine seismic surveying equipment and seismic data processing techniques in order to obtain accurate, high-resolution seismic images of subterranean formations located beneath a body of water. High-resolution seismic images are used to determine the structure of subterranean formations, discover hydrocarbon deposits, and monitor hydrocarbon deposits during production. A typical marine seismic survey is carried out with a survey vessel that tows one or two sources and a number of streamers below the surface of the body of water. A typical source comprises an array of source elements, such as air guns. The streamers are elongated cable-like structures towed behind the survey vessel in the direction the survey vessel is traveling. Each streamer includes a number of receivers that generate seismic data in response to detecting pressure and/or particle motion wavefields. The streamers are arranged substantially parallel to one another to form a seismic data acquisition system. The survey vessel contains seismic acquisition equipment, such as navigation control, source control, seismic receiver control, and seismic data recording equipment.
A typical marine seismic survey is carried out by activating the one or more sources above a subterranean formation. Each activation produces acoustic energy that expands outward in all directions. A portion of the acoustic energy travels downward through the body of water and into the subterranean formation. At each interface between different types of rock and sediment, a portion of the acoustic energy is refracted, a portion is transmitted, and another portion is reflected from each interface into the body of water to propagate toward the free surface. The portion of the acoustic energy reflected into the body of water is measured by the receivers and is recorded as seismic data that is processed to generate seismic images of the subterranean formation.
In recent years, seismic data modelling has become an important tool in marine seismology. Seismic data modelling techniques simulate propagation of acoustic energy in a model subterranean formation and generates synthetic seismic data collected by synthetic receivers. Seismic data modelling techniques that include actual geological information about a subterranean formation may be used to generate synthetic seismic data that is used to identify features of the subterranean formation. For example, the synthetic seismic data may be used to estimate rock properties of various layers of the subterranean formation and determine whether or not oil, gas, or water reservoirs are present in the subterranean formation. Seismic data modelling may be applied to a model subterranean formation in order to generate synthetic seismic data that is used to test, or benchmark changes to, seismic data processing and imaging techniques. Seismic data modelling may also be used to design marine seismic surveys. Having a good model subterranean formation may be useful in transitioning from a two-dimensional survey to a three-dimensional survey or designing a new marine seismic survey if seismic data obtained in a previous marine seismic survey failed to meet certain requirements.
Typical seismic data modelling techniques used to generate synthetic seismic data of a model subterranean formation located beneath a body of water are based on an assumption that the body of water through which acoustic energy propagates is a time invariant (i.e., stationary) medium. However, actual bodies of water are constantly in motion due to water currents and weather, which has an effect on the propagation of acoustic energy between the free surface of the body of water and the subterranean formation. Real seismic data collected in an actual marine seismic survey records the effects of this constantly changing environment. As a result, synthetic seismic data produced by typical seismic data modelling techniques may not accurately compare with real seismic data collected in an actual marine seismic survey and, therefore, may not always be relied upon to estimating rock properties of subterranean formation, identify the contents of a subterranean reservoir, and design a marine seismic survey.